A conventional pipe fastener 1 is shown in FIG. 1 and generally includes a slot 101 defined through a first end 103 thereof and a second end 102 of the fastener 1 extends through the slot 101 so as to fasten a hose to a connector (both not shown). When unfastening the fastener 1, a tool 2 as shown in FIG. 2 is used which is cooperated with a device 4 to separate the first and second ends 102, 103 to loosen the fastener 1. The tool 2 includes two handles pivotably connected with each other and a cable unit 3 has one end fixed to one protrusion extending from one of the two handles and the other end of the cable unit 3 is connected to the device 4 which is operated by pivoting the two handles toward each other. The device 4 can reach a deep and narrow space to unfasten the target fastener. The device 4 includes a base 401 and a movable member 402 is slidably mounted to the base 401. A fixed plate 404 extends from an end of the base 401 and a movable plate 405 extends from the movable member 402. By pulling the cable unit 3, the movable member 402 is moved relative to the base 401 so as to adjust the distance between the fixed plate 404 and the movable plate 405 to separate the first and second ends 103, 102 of the fastener 1. Nevertheless, the distance between the fixed plate 404 and the movable plate 405 is fixed when the cable unit 3 is not yet pulled, so that if the distance between the first and second ends 103, 102 of a fastener 1 is smaller than the distance between the fixed plate 404 and the movable plate 405 is fixed when the cable unit 3 is not yet pulled, the device 4 is useless. In other words, the user has to prepare a plurality of devices with different distances between the fixed plate 404 and the movable plate 405 so as to unfasten the fasteners 1 of different sizes.
The present invention intends to provide an unfastening device for unfastening fasteners that includes several pairs of clamp plates so that the device is able to deal with a wide range of distance between the two ends of fasteners.